Dust from comet is unveiled

The first image of comet dust plucked from space shows a tiny, dark blob.

But to University of Washington astronomer Don Brownlee, it's more stunning than a diamond.

"You're seeing the very first, absolutely identified comet particle that has ever been seen," Brownlee said Thursday at a NASA briefing in Houston where photos showing the cosmic cargo from the Stardust mission were released.

The pictures revealed the way the tiny particle — less than a thousandth of an inch across — burrowed into the translucent collector material called aerogel and then stopped. In close-up view, the particle almost glitters.

"It's a crystalline silicate grain," said Brownlee, principal investigator for the $212 million mission to grab comet dust and bring it back to Earth. "This is great; we've already got scientific results."

And it's barely the tip of the iceberg. The particle shown Thursday was embedded in a chip of aerogel that broke off the collector. Brownlee estimated the collector will yield up to 1 million particles of all sizes. The largest could measure up to four hundredths of an inch across.

The Stardust capsule parachuted to the Utah desert early Sunday.

Information

Stardust online: More information, including pictures of scientists working with the Stardust collector is at: www.nasa.gov/mission_pages/
stardust/main/index.html

Since the comet-dust collector was opened Tuesday at Johnson Space Center in Houston, scientists have been working to photograph and record comet particles embedded in the collector. They will begin plucking some of the grains out next week. More than 150 researchers around the world have requested samples.

"You'll see a lot of information coming out quickly from these samples," said Michael Zolensky, who runs the special NASA clean room where the comet dust is being processed.

A single grain can prove fodder for months or years of study, Brownlee said.

By studying comets, which are believed to be relatively unchanged since their formation 4.5 billion years ago, scientists hope to learn more about the origin of the solar system.

On Thursday, the National Aeronautics and Space Administration launched the world's first mission to Pluto, which Brownlee said has a lot in common with comets. Though Pluto is much bigger, it orbits in the same icy reaches of the solar system as most comets, including Wild-2, the comet with which Stardust rendezvoused.

Scientists also hope to use particles captured by Stardust to study the death and birth of stars — and they're asking for the public's help.

The backside of the Stardust collector was used to snag interstellar dust during the spacecraft's seven-year, 2.9 billion-mile journey. Even tinier than comet grains, interstellar dust is believed to be the remnants of distant star explosions.

Scientists estimated Stardust may have captured about 100 of the particles, which average about a millionth of a meter in diameter.

Pinpointing those particles will be time-consuming.

Volunteers who participate in the Stardust@home project via computer will scan enlarged photos of the aerogel, looking for the tiny tracks left by interstellar particles as they plunged into the lightweight solid. Amateur scientists who find particles will get to name them and will be listed as co-authors on any studies conducted on their discovery.

About 65,000 people have signed up, Zolensky said, adding, "We're hoping for many more."

The effort is expected to start in March, when the aerogel pictures will be posted on the Web. More information is available at: stardustathome.ssl.berkeley.edu.

Sandi Doughton: 206-464-2491 or sdoughton@seattletimes.com